Valve lifter



Dec. 6, 1960 A. F. DAVIS ETAL VALVE LIFTER Filed June 29, 1959 IN VEN T0R5 United States Patent VALVE LIFTER Albert F. Davis, Grand Rapids, andCharles H. Palmer,

Holland, Mich., assignors to General Motors Corporation, Detroit, Mich.,a corporation of Delaware Filed June 29, 1959, Ser. No. 823,572

20 Claims. (Cl. 123-90) This invention relates to a composite valvelifter and similar articles and to an improved method of making same.

A specific object of this invention is to provide a new and improvedvalve lifter of the mechanical type formed of a tubular steel bodymember having an imperforate push rod seat and an end closingwear-resistant metal foot piece secured to the tubular member by abrazed joint having a bonding interface formed from areas having anaccurately controlled surface finish.

Among other objects of this invention are: to provide a method offorming an improved composite article, such as a valve lifter body orsimilar article; to provide a more economical improved valve lifterhaving an imperforate push rod seat integral with the tubular bodythereof and to provide an improved method of forming composite valvelifter bodies and similar articles which lends itself to high productionoperation under conditions resulting in excellent metallurgical controland maximum uniformity of the product. 7

In accordance with the invention there is provided a compositemechanical valve lifter or similar article having an imperforate pushrod seat member adjacent one end of a tubular body member, preferablyintegral therewith. A foot piece of cast iron or the like having anaccurately controlled surface finish is brazed to the other end of thetubular body member. The end cap or foot of the valve lifter engages thecam or other operating member and must be formed of a hard,wear-resistant material, such as cast iron while the body member can beof a low carbon steel. Excellent results have been obtained by brazingthe foot piece to the body member with a copper-tin alloy. The footpiece is first coated with the alloy and then assembled with the tubularbody member. The assembled parts are thereafter heated to a sufficienttemperature to melt the copper coating and suitably bond the partssecurely together.

Reference is made herewith to the accompanying drawing, in which:

Figure 1 is a fragmentary elevational view, in partial section, showinga tubular body member for a valve lifter or similar article and an alloycoated foot piece; and

Figure 2 shows. a sectional view taken longitudinally through amechanical valve lifter, such as can be formed in accordance with thepresent invention.

Referring now to Figure l, a valve lifter generally comprises a tubularbody member 10 to one end of which a cast metal foot or end cap 12 issecured. The end of the tubular body member has a bore 14 of suitabledimension to snugly receive the end cap 12. The end cap is a generallycylindrical member, a portion 16 of which is of a reduced diameter andslightly tapered for insertion in close-fitting relationship within thebore 14 of the tubular body member. The reduced diameter portion 16gives rise to a shoulder 18 on the end cap 12 which abuts the endsurface 20 of the tube when the end cap and tubular body member areassembled.

The tubular body member of a mechanical valve lifter; or the like, canbe cold formed from SAE 1010, SAE 1016 or equivalent low carbon steel.As shown in connection with Figure 2, the steel is extruded to form atubular body 10 having, adjacent one end, an imperforate integraltransverse wall 22 in which is formed a push rod seat 24. Upon assemblyof the parts 10 and 12, a closed chamber 26 is formed in the lifter.

The foot piece or end cap for a valve lifter is preferably made of ahard, wear-resistant material, such as cast iron or the like. One suchmaterial which can be used is as follows:

Generally the composite valve lifter is made by brazing the cast ironfoot piece 12 to the tubular body member 10. In order to obtain asatisfactory high strength joint between the foot piece and the tubularbody member, it has heretofore been believed necessary to resort to theuse of atmosphere for protection against oxidation of alloy or jointsurfaces for good bonding. Heretofore in the presence of at least oneaperture in the push rod seat member or wall 22, flushing or purging airfrom the interior 24 of the valve lifter was necessary. It has now beenfound that an improved valve lifter can be obtained if it is formed withan imperforate transverse wall. Moreover, a highly satisfactory brazedjoint is obtained without purging the exterior of the lifter if thesurface finish of the mating interfacial bonding areas is accuratelycontrolled. By making a valve lifter in accordance with our inventionnot only is the requirement for atmospheric protection of the jointduring brazing materially minimized but, in certain instances, it ispossible to bond the two parts entirely without the use of anyprotective atmosphere. Thus not only is the resultant product improvedbut also its method of manufacture.

It is also desirable to form a sealed chamber 26 in the valve litter inorder to maintain a constant light weight of the valve lifter and toinsure unIform weight distribution of the plurality of valve liftersused in an engine. Although it is extremely advantageous to form a valvelifter having the sealed inner chamber, heretofore it was not possibleto make such a satisfactory valve lifter with an integral imperforatetransverse wall in a tubular body member.

We have now found, however, that if the relative surface finishes of themating surfaces of the tubular body member and the foot piece areaccurately controlled, an excellent brazed joint can be formed. Whenusing a tubular body member having a surface finish of approximately 10micro inches R.M.S. to micro inches R.M.S., excellent brazed joints canbe obtained if the surface of the cast iron foot piece is maintainedbetween approximately 70 micro inches R.M.S. and micro inches R.M.S. andthe amount of brazing alloy accurately controlled. When using a tubularbody member having the described surface finish a satisfactory brazedjoint, in certain instances, may be obtained using a surface finish aslow as approximately 60 micro inches R.M.S. More: over, in someinstances, it may be possible to obtain satisfactory results withsurface finishes as high as 200 micro inches R.M.S. on the cast ironfoot piece.

It is also contemplated that the steel body member can be made with asurface finish exceeding 80 micro inches R.M.S. In such instance thesurface finish of the cast iron foot piece can be. correspondinglyreduced. If the-bonding area of the tubular body member had a surfacefinish in excess of 100 micro inches'R.M.S., the surface finish of themating portion of the end cap could be as low as 50 micro inches R.M.S.In general, however, we prefer to employ a tubular body member having asurface finish below approximately 100 micro inches R.M.S.

The brazing material may be applied to the parts in a variety of ways,such as in powdered form or a solid ring to obtain a suitable brazedjoint. However, an especially durable bond can be obtained in formingour valve lifter if the brazing alloy is applied as a coating on thefoot piece 12 in accordance with the method set forth in the previouslyfiledpatent-application Serial No. 754,822, filedAugust 13, 1958, in thenames of John Dornbos, Ell-en-L'. Karchnerand Charles H. Palmer andassigned to the assignee of the present invention.

The previously filed application describes using an electrodepositedcopper-tin alloy coating on the cast iron foot piece as the sourceofbrazing material to the bonding interface. When brazing the alloycoated cast iron foot piece to the body-member by induction heating, theuse of a protective atmosphere is not only minimized but may also evenbe eliminated.

By using the copper-tin alloy coating on a cast iron end cap for thedesired surface finish, the foot piece can be brazed to a tubular bodymember having an imperforate transverse wall simply and economicallywith a joint as strong as a joint made with the use of a protectiveatmosphere. Exceedingly satisfactory joint strength was achieved withthis type of alloy which has an especially uniform melting point.Moreover, maximum uniformity of the product and excellent metallurgicalcontrol of the bonding can be achieved when the thickness of the coatingand composition of the brazing alloy is accurately controlled.

More particularly by using an electroplating bath, such as hereinafterset forth, the composition of a copper-tin brazing alloy having anunusually high tin content can easily be accurately controlled undercommercial high production conditions. A copper-tin brazing alloycontaining about to 60%, by weight, tin and about 40% to 80%, by weight,copper has been satisfactory in producing a strongly bonded compositeassembly. However, in general, it is preferable to use an alloy having acomposition of about to by weight, tin and about 60% to 75%, byweight,-copper. This latter brazing alloy is especially preferred due toits uniform melting point temperature in the range'from about 1360 F. to1550 F. while in the former alloy the melting point temperature variesfrom about 1360" F. to l650 F. It is especially desirable to employ abrazing alloy which uniformly melts to form a bond of superior strengthand which provides a uniform impervious joint.

As hereinbefore mentioned, maximum uniformity of the product andexcellent metallurgical control of the bonding can be achieved when thethickness of the coating and the composition of the brazing alloy isaccurately controlled. The thickness of the coating is easily controlledvery precisely when the coating is formed by electrodeposition. Thenature of a copper-tin alloy coating of the composition, such ashereinbefore described, can be easily and precisely controlled byelectrodepositing the alloy from an aqueous alkaline coppercyanidepotassium stannate bath solution. We have found such anelectroplating solution canbe effectively used to deposit an alloy ofour preferred composition if the relative proportion by weight of freepotassium cyanide to the potassium cupro cyanide in the bath ismaintained at about 0.8 to 1 respectively. A cast iron foot piece of avalve lifter, 'forexample, can be coated with a copper-tin alloy ofsuitable composition using a bath solution which in operation is asfollows:

Ounces per gallon A wear-resistant metal foot piece is placed in theabovedescribed plating solution and the copper-tin alloy iselectrodeposited at a bath temperature of about F. to l70 F. using acurrent density from approximately 10 amperes per square foot to 70amperes per square foot.

The electrodeposition is continued until a sufficient plate thickness isachieved, preferably at least about 0.0008 inch. The specific depth orthickness of the electrodeposited layer of brazing alloy is dependentupon the roughness of the casting surface, the fit or clearance desiredbetween the tubular body member and the end cap, objections to an excessof brazing alloy, etc. In general, plating thicknesses of at least about0.0008 inch are used to form a satisfactory bonding while thicknesses inexcess of about 0.00 15 inch are undesirable. Coating thicknessessubstantially greater than about 0.0015 inch tend to contribute to adisplacement of the end cap during brazing. Moreover, excessivethicknesses may produce a poor bond which may be deleteriously affectedin subsequent hardening operations. Moreover, if an excess of brazingalloy is present, it may flow during the brazing operation intoundesired areas.

We have found that the composition of the brazing alloy can moreprecisely be contained within the preferred limits when using a platingbath which, as formed, is as follows:

Ounces per gallon Free KCN n 2.5-3.5 KCu(CN) 3.0-3.5 KOH 0.5l.0K2SI'1(OH)6 A satisfactory coating is obtained when electrodepositingthe bronze alloy from the above bath at a temperature of from about F.to F. using a cathode current density of about 10 amperes per squarefoot to 15 amperes per square foot.

The alloy coated end piece is assembled with the tubular body member towhich it is to be secured to form a composite assembly. The assembledparts are then heated in a furnace to about 1550 F. to about 1700" F.for a duration of about 30 minutes to about 60 minutes. However, ifinduction heating is used, the assembly is preferably heated to abrazing temperature of approximately 1800" F. to 1900 F. forapproximately 30 seconds.

Iigher temperatures used in the induction heating require a shorterduration of heating in order to approximate essentially the same flowand diffusion of the alloy into the parts as produced by furnaceheating. An insufficient brazing temperature or duration of thetreatment is characterized by a low strength bond in which there hasbeena non-uniform flow of the brazing alloy.

As previously pointed out, the requirement of using a protectiveatmosphere to obtain-a satisfactory brazed joint is not only materiallyreduced but may even be eliminated. When brazing the parts by inductionheating, the protective atmosphere need not be used. If furnace brazingthe parts, it is desirable to use a protective atmosphere to some extentto avoid excessive scaling, spalling, etc. of the outer surfaces of theparts. No purging of the body member is necessary, however. Oneprotective atmosphere which can be used has the following analysis: 20%carbon monoxide, 40% hydrogen and 40% nitrogen, all proportions byvolume. However, substantially pure mixtures of hydrogen, carbonmonoxide, nitrogen, helium, argon, etc., can also be used.

We have additionally found that the strength of the bond between the endcap 12 and the tubular body member is particularly is in an extremelyclose fitting relationship with the tubular body member. Accordingly, itis especially desirable to have the diametrically smaller portion 16 ofthe coated end cap be of at least about the same dimension as theconfiguration of the bore 14 of the tubular body member. We have foundthat by press fitting the alloy coated end cap 12 within the end of thetubular member, an intimate contact of the bonding surface is obtainedwhich facilitates uniform distribution and flow of the brazing alloyduring brazing. The intimate contact and resultant uniform flow areparticularly effective in producing an imperforate joint or bond betweenthe members. Highly satisfactory results are obtainable when thediametrically smaller portion 16 of the end cap 12 for a valve lifterhaving an outer diameter of about 0.875 inch is at least about 0.004inch greater than the inner diameter ofthe tubular member. With thisrelative construction the end cap must be press fitted on the end of thetubular member in the assembly of the composite article prior tobrazing. In general, the limiting dimension for the maximum diameter ofthe smaller portion of the end cap is determined by the strength of thetubular member. In most instances, this maximum limit is approximately0.028 inch.

The tubular member of a typical valve lifter, such as shown in Figure 2,has an outer diameter of approximately 0.90 inch and an enlarged taperedbore adjacent one end of approximately 0.78 inch in maximum diameter forreceiving the end cap. The tapered part of the coated end cap has atransverse dimension of between approximately 0.0008 inch and 0.0015inch greater than that of the bore of the tubular member. The smallerportion of the end cap is compressed into the enlarged bore of thetubular member so that the shoulder of the end cap abuts the end surfaceof the tubular member.

In making a valve lifter, such as just described, the foot piece wascleaned prior to applying the alloy coating to remove rust, dirt,grease, etc. An initial cleaning to remove foundry sands and rust can beeffected by a wheel-abrate cycle of about 10 minutes using about a 500pound load. The part can then be degreased, if necessary, in the usualway as by means of solvents such as trichloroethylene or the like. Afterdegreasing the part, it can then be pickled in a suitable acid solutionin the known and accepted manner for such cleaning, such as by immersionfor about two minutes in an aque ous solution containing 9% to 10%muriatic acid.

After suitable cleaning the part was rinsed to remove the acid adheringthereto and preferably placed in an aqueous solution containing about2.5 ounces to 3 ounces of potassium cyanide per gallon of water. Afterimmersion in the potassium cyanide solution for approximately 2 minutesthe part was removed therefrom and directly placed in the plating bath.

The end cap was placed in a bronze plating solution which, as formed,was compounded to deposit a bronze alloy containing about 30%, byweight, tin and about 70%, by weight, copper. This plating solution wasformed with de-ionized Water, as follows:

Ounces per gallon Free KCN 3.0 KCu(CN) 3.0 KOH 0.4 K Sn(OH) 13.5

increased when the end cap The assembly was then placed in a brazingfurnace under a temperature of approximately 1600 for approximately 40minutes under a protective atmosphere, such as hereinbefore described.It was removed from the brazing furnace and subsequently cooled underthe protective atmosphere.

Due to the continuous succession of shocks and various dynamic stressesto which a valve lifter is subjected, it is readily apparent that anexceptionally strong bond ing of the end cap to the body member must beobtained. Moreover, in commercial applications, it is of extremeimportance that this bond be consistently uniformly but economicallyformed under production conditions. By uniformly coating the bondingsurface of the end cap with the brazing alloy, it is inherentlyuniformly distributed throughout the bonding interface when the parts tobe joined are assembled. Moreover, a separate step in the assemblyoperation of each composite unit is omitted, thus expeditingmanufacturing operations. By coating the end caps as large groups, onlyone coating step is necessary for a great many parts.

Although this invention has been described in connection with certainspecific embodiments thereof, no limitation is intended thereby exceptas defined in the appended claims.

We claim:

1. A valve lifter comprising a tubular member, an imperforate integraltransverse wall within said tubular member and an end cap, said end capbeing brazed to one end of said tubular member.

2. A valve lifter comprising a tubular member, an imperforate integraltransverse wall within said tubular member and an end cap, a portion ofsaid end cap extending within one end of said tubular member andsuitably brazed to said tubular member.

3. A valve lifter comprising a tubular member, an imperforate transversewall within said tubular member and an end cap, a portion of said endcap extending within one end of said tubular member and suitably brazedto said tubular member with a copper-tin alloy, said alloy supplied asan electrodeposited coating on said end cap.

4. A composite article comprising a tubular member, an imperforatetransverse wall in said tubular member and an end cap on said tubularmember having a portion thereof extending into said member, said end capbonded to said member by a suitable brazed joint having a bondinginterface, said interface formed from mutually contacting areas, one ofwhich has a surface finish below about micro inches R.M.S. and the otherof which has a surface finish of about 60 micro inches R.M.S. to 200micro inches R.M.S.

5. A composite article comprising a tubular member, an imperforatetransverse wall in said tubular member and an end cap on said tubularmember having a portion thereof extending into said member, said end capbonded to said member by a suit-able brazed joint having a bondinginterface, said interface formed from mutually contacting areas, one ofwhich has a surface finish below about 100 micro inches R.M.S. and theother of which has a surface finish of about 70 micro inches R.M.S. tomicro inches R.M.S.

6. A composite article com-prising a tubular member, an imperforatetransverse wall in said tubular member and an end cap on said tubularmember having a portion thereof extending into said member, said end capbonded to said member by a suitable brazed joint having a bondinginterface, said interface formed from mutually contacting areas, one ofwhich has a surface finish of about 10 micro inches R.M.S. to 80 microinches R.M.S. and the other. of which has a surface finish of about 70micro inches,R.M.S.,to 160 micro inches R.M.S.

7'. A composite article, comprising-a tubular-,member,

an imperforate transverse wallin saidtubular member and an end cap onsaid tubular member having a por-,

of extending into said member, said end cap bondedv to said member by asuitable brazed joint having a bonding interface, said interface formedfrommutually contacting areas, one of which has a surface finish belowabout 100 micro inches R.M.S. and the other of. which has a surfacefinishof about 60 micro inches R.M.S. to 200 micro inches R.M.S.

9. A valve lifter comprising a tubular member, animperforate transversewall, a push rod seat in said Wall and an end cap on said member havinga portion thereof extending into said member, said end cap bonded tosaid member by a suitable brazed joint having a bonding interface, saidinterface formed from end cap and member mutually contacting areas whichrespectively have surface finishes of about 70 micro inches R.M.Sfto 200micro inches R.M.S. and 10 micro inches R.M.S to 100 micro inches RM.S.

' 10. A valve lifter comprising a tubular member, an imperfor-atetransverse wall, a push rod seat in said wall and an end cap on saidmember having a portion thereof extending into said member, said end capbonded to said member by a suitable brazed joint having a bondinginterface, said interface formed from mutually contacting areas, one ofwhich has a surface finish below about 100 micro inches R.M.S. and theother of which has a surface finish of about 60 micro inches R.M.S. to200 micro inches R.M.S., said areas being bonded by an alloy containing,by weight, about 20% to 60% tin and 40% to 80% copper, supplied as anelectrodcposited coating on said end cap.

11. The method of making a composite article which comprises forming atubular member having at one end a surface adapted to receive an endcap, forming an imperforate transverse wall in said tubular member,forming an end cap having a surface for mating engagement with thesurface of said tubular member, applying a brazing alloy to one of saidsurfaces, assembling said end cap with said tubular member to form acomposite article, heating said composite article to abrazingtemperature for a sufiicient duration to suitably bond said endcap to said tubular body member by means of said brazing alloy andcooling said composite article.

- 12. The method of making a composite article which comprises forming atubular member having at one end a surface adapted to receive an endcap, forming an integ-ral imperforate transverse wall in said tubularmember, forming an end cap having a surface for mating engagement withthe surface of said tubular member, applying a brazing alloy to one ofsaid surfaces, assembling said end cap with said tubular member to forma composite article, heating said composite article to a brazingtemperature for a suificz'ent duration to suitably bond said end cap tosaid tubular body member by means of said brazing alloy and cooling saidcomposite article.

13. The method of making a composite article which comprises forming atubular member having at one end a surface adapted to receive an endcap, forming an imperforate transverse wall in said tubular member,forming an end cap having a surface for mating engagement with thesurface of said tubular member, electrodepositing a coating of acopper-tin alloy on said end cap surface, assembling said end cap withsaid tubular member.- to; orm,a compositearticle, heating said compositearticle to a brazing temperature for a sufficient duration to suitablybond said end cap to said tubular body member by means of said brazingalloy and cooling said 1 composite article.

14. The method of making a composite article which comprises forming atubular member having at one end a surface adapted to receive an endcap, forming an imperforate transverse wall in said tubular member,forming an end cap having a surface for mating engagement with thesurface of said tubular member, one of said surfaces having a surfacefinish below about 100 micro inches R.M.S., the other of said surfaceshaving a surface finish.

of about 60 micro inches R.M.S. to 200,micro inches R.M.S., applying abrazing alloy to one of said surfaces, assembling said end .cap withsaid tubular member to form a composite article, heating said compositearticle to a brazing temperature for a suflicient duration to suitablybond said end cap to said tubular. body member by means of said brazingalloy and cooling said composite article.

15. The method of making a composite article which comprises forming atubular member having at one end a surface adapted to receive an endcap, forming an imperforate transverse wall in said tubular member,forming an end cap having a surface for mating engagement with thesurface of said tubular member, one of said surfaces having a surfacefinish below about 100 micro inches R.M.S., the other of said surfaceshaving a surface finish of about 70 micro inches R.M.S. to 160 microinches R.M.S., applying a brazing alloy to one of said surfaces,assembling said end cap with said tubular member to form a compositearticle, heating said composite article to a brazing temperature for asufficient duration to suitably bond said end cap to said tubular bodymember by means of said brazing alloy and cooling said compositearticle.

16. The method of making a composite article which comprises forming atubular member having at one end a surface adapted to receive an endcap, forming an imperforate transverse wall in said tubular member,forming an end cap having a surface for mating engagement with thesurface of said tubular member, one of said surfaces having a surfacefinish of about 10 micro inches R.M.S. to micro inches R.M.S.. the otherof said surfaces having a surface finish of about 70 micro inches R.M.S.to 160 micro inches.R.M.S., applying a brazing alloy to one of saidsurfaces, assembling said end cap with said tubular member to form acomposite article, heating said composite article to a brazingtemperature fora sufficient duration to suitably bond said end cap tosaid tubular body member by means of said brazing alloy and cooling saidcomposite article.

17. The method of making a composite article which comprises forming atubular member having at one end a surface adapted to receive anvendcap, said surface having a surface finish below about micro inchesR.M.S., forming an imperforate .transverse wall in said tubular member,forming an end cap having a surface for mating engagement with thesurface of said tubular member, said end cap surface having a surfacefinish of about 60 micro inches R.M.S. to 200 micro inches R.M.S.,applyinga brazing alloy to one of said surfaces, assembling said end capwith said tubular member to form a composite article, heating saidcomposite article to a brazing temperature for a sufficient duration tosuitably bond said end cap to said tubular body member by means of saidbrazing alloy and cooling said composite article.

18. The method of making a valve lifter which comprises forming atubular member having at one end a surface adapted to receive an endcap, said surface having a surface finish below about 100 micro inchesR.M.S., forming an imperforate transverse wall in said tubular member,forming an end cap having a surface for mating engagement'with thesurface of said tubular member, said end cap surface having a surfacefinish of about 70 micro inches R.M.S. to 160 micro inches R.M.S.,applying a brazing alloy to one of said surfaces, assembling said endcap with said tubular member to form a composite article, heating saidcomposite article to a brazing temperature for a sufficient duration tosuitably bond said end cap to said tubular body member by means of saidbrazing alloy and cooling said composite article.

19. The method of making a valve lifter which comprises forming atubular steel member having at one end a surface adapted to receive anend cap, said surface having a surface finish below about 100 microinches R.M.S., forming an imperforate transverse wall in said tubularmember, forming an end cap having a surface for mating engagement withthe surface of said tubular member, said end cap surface having asurface finish of about 70 micro inches R.M.S. to 160 micro inchesR.M.S., coating said end cap with a brazing alloy containing, by weight,about 20% to 60% tin and 40% to 80% copper, assembling said coated endcap with said tubular member to form a composite article, heating saidcomposite article to a brazing temperature for a sufficient duration tosuitably bond said end cap to said tubular body member by means of saidbrazing alloy and cooling said composite article.

20. The method of making a valve lifter which comprises forming atubular steel member having at one end a surface adapted to receive anend cap, said surface having a surface finish of about 10 micro inchesR.M.S. to 80 micro inches R.M.S., forming an imperforate transverse wallin said tubular member, forming an end cap having a surface for matingengagement with the surface of said tubular member, said end cap surfacehaving a surface finish of about 70 micro inches R.M.S. to 160 microinches R.M.S., coating said end cap with a brazing alloy containing, byweight, about 20% to 60% tin and 40% to 80% copper, assembling saidcoated end cap with said tubular member to form a. composite article,heating said composite article to a brazing temperature for a sufficientduration to suitably bond said end cap to said tubular body member bymeans of said brazing alloy and cooling said composite article.

References Cited in the file of this patent UNITED STATES PATENTS2,178,724 Hoern Nov. 7, 1939

